The double-axis electromagnetic stirrer is an electromagnetic stirrer that can effectively convey the magnetic fluxes of a vertical electromagnetic field and a rotational electromagnetic field to liquid metal inside a container and set the liquid metal in rotational motion and vertical motion when these electromagnetic fields are superposed on each other.
Conventionally, as the double-axis electromagnetic stirrer, techniques described in Patent Document 1 and Patent Document 2 are known.
In these techniques, as shown in FIG. 8, a vertical electromagnetic field generating coil 13 is circumferentially provided on the outer side of a cylindrical container 11 along the vertical direction, and a rotational electromagnetic field generating coil 12 is circumferentially provided on the outer side of the container 11. The rotational electromagnetic field generating coil 12 sets liquid metal in the container 11 in rotational motion, and the vertical electromagnetic field generating coil 13 sets the liquid metal in vertical motion.
However, the techniques described in Patent Document 1 and Patent Document 2 have a problem that the magnetic fluxes are leaked and as the result it is difficult to obtain a sufficient stirring force.
On the other hand, as a technique that prevents the leakage of magnetic flux to increase stirring force, a technique is described in Patent Document 3 in which an iron core is inserted between rotational electromagnetic field generating coils and between vertical electromagnetic field generating coils. “FIG. 2” of Patent Document 3 is shown in FIG. 9.
This drawing shows an example in which vertical electromagnetic field generating coils 111 are arranged on the inner side and rotational electromagnetic field generating coils 113 are arranged on the outer side. In other words, this stirrer has a container 103 for liquid metal, the vertical electromagnetic field generating coils 111 arranged along the vertical direction of the container 103, the rotational electromagnetic field generating coils 113 circumferentially arranged on the outer side of the vertical electromagnetic field generating coil 111, and an iron core 109 that is inserted into the center of the rotational electromagnetic field generating coil 113 and has comb teeth extended to the inner surface of the vertical electromagnetic field generating coil 111.
FIG. 10 shows a diagram depicting “FIG. 3” of Patent Document 3.
This drawing shows an example in which vertical electromagnetic field generating coil 111 are arranged on the outer side, and rotational electromagnetic field generating coils 113 are arranged on the inner side.
Thus, the technique described in Patent Document 3 has less leakage of magnetic flux than that of the technique with no iron core. However, when taking a look at stirring force for liquid metal inside the container, the stirring force is not so dramatically improved as compared with the case of providing the iron core.    Patent Document 1: JP 2003-220323 A    Patent Document 2: JP 2007-144501 A    Patent Document 3: JP 1979-163729 A